Fix few issues in TPU util functions (#444)
Fix few issues in TPU util functions (#444)

* Fix a couple of typos in setup_tpu, cleanup_tpu
* Use "./ctpu" instead of "ctpu", because in some VM shells, "./ctpu" is needed to locate downloaded ctpu binary
* Add some logging for future debugging

Tested:
ran with PerfZero in the same cloud VM we have been using for TPU benchmarks and observed TPU created and later deleted
tensorflow/benchmarks,tensorflow/benchmarks